Explosive composition containing vermiculite



Patented Dec. 4, 1951 UNITED; STATES;

EXPLDSIVE COMPOSITION CONTAINING VERMICULITE Austin Maurice'Gummings, Woodbury, N. .L, as-

signor to El. du Pont de Nemours8rCompany, Wilmington, D na corporation of Delaware No'Dra'wing. Application October 23, '1947;

Serial No. 781,759

2 claims..... (01. 52--11)' Thisinvention relates to an improved explosive H composition of the vnon-nitroglycerin type ,in i

which nonormally liquid 'componentris present.

Asris well known, the: nitroglycerin dynamites 1 normally include, .in addition to this ingredient,

onea'or more oxidizing agents, and combustible oxygen-acceptors such as wood." pulp or various meals, these-latter materials functioning: also as absorbentsfor the nitroglycerinp so that no exudation shall take place. Explosives haverbeen developed that are free 1 from liquid ingredients and that are based on ammonium nitrate-as the explosive ingredient: explosive or nonexplosive solid inaterials being :present that are deficient in oxygen and that sensitize the ammonium nitrate and substantially balance itwith respect to oxygen.- The Nit'ramon type of explosive is a relatively recent development in such exp1o-" sive's; as disclosedin USP'1,992;21'7. This bla'st ing agent is of a low order of sensitivityisuch that it is not capable of detonation by means of a commercial blasting cap but'can be brought to detonation 'readily'by a stronger 1 booster charge. While this latter blasting agent contains ingredients that are-highly susceptible to the eiiect of water and moisture;it iscompletely protected therefrom by "tight enclosure' withina' metal container.

Cap -insensitive ammonium nitrate explosives of the type described must be controlled within predetermined close limits as to density, if satis-' factory performance isto be assured; One'method used for obtaining this control is. by the in-' clusi'on-in the composition of a relatively low-'- density organic meal such as a comminutedflaked corn product or its substantial equivalent. Such organic materials .have notbeen satisfactory, however, inasmuch as they increase the combustibility of the product and thus affect the safety properties adversely, especially when elevated temperatures mayr'be employed iduring manufacture and incorporation- 4.

An'object of the present invention is an tim 1- proved explosive composition of the non-nitros glycerin type, in which ammonium nitrateisthe principal explosive ingredient. A furtheriobject is such a composition of a low, order of sensitive- 2 mess to detonation and of a relatively high density. A still further object is such an ammonium nitrate composition in which a low density ingredient is included that facilitates satisfactory density control but has no unfavorable efiect on the flammability and safety properties. Additional objects will be disclosed as the invention is described at "greater'lengthhereinws.

after. I

I have -found thatthe foregoing 'objects'are accomplished, and a highly desirable product;:- obtained, when I employ an explosive composition free from normally liquidingredients, explosive or non-explosive; and. comprising at least one-inorganicoxidizihg agent, at least, one organiccombustible ingredient functioning--as--an=-: oxygen-acceptor" and as a sensitizer= for the oxidizing agent, and a relativelysmall proportion of a low density,'expanded hydrated silicate;

'I he inorganic oxidizing agentwillpreferably ,be'v

ammoniumnitrate because of its known proper---- 1 ties'and its ability to enter into explosive reactionseifecti-vely. Various organic sensitizers may i be employed such'as parafiin, nitrotoluene, coal,-

and the like; .Asthe low density silicate; we find the mineral vermiculite particularly. desirable in its expanded-or exfoliated form, as a result-of treatment at high temperatures;

The following composition illustrates one embodiment ofwan ammonium nitrate explosive formula in accordance with the disclosures of the present invention. I It will be'understood that the composition given is by way of exampleonly.

and is not to be taken as limiting in any way. 2

In preparing the...abo.ve mixture, ammonium. nitrate of the predetermined degree of fineness. wasiblended with the sodiumnitrate andheatedto 54 C., and paraffin was then added andimixed "fori10 minutes. ...Dinitrotoluene .was added/and mixed for an additional 10 minutes, then; the vermiculite, .with. additionaL. 5. minute: mixing.

Thelfinishedmixture was .dischargediat a tem;

perature of. around..63! C; I At a density of 1101)}7, the composition was insensitiveto the action of l seven-No. 8 blastingwcapsb When packed into".

tightly-sealedcans, 4 in. x 24 in. injdimensions, .l and primed with i a suitable booster, the; i ,t

explosion was propagated from one can to another with an undiminished velocity of detonation of around 3400 meters per second. To illustrate the improvement with respect to flammability by the replacement of organic low density combustibles by the expanded vermiculite, the following results are conclusive on comparale formulas containing different low density gredients:

Ignition Low Density Ingredient Time at Hours iked Com Product; 7 gasse Pith 83-6 pended vermiculite 24 The present invention is applicable to various"- pes of explosive compositions that are ee from liquid ingredients, whether liquid ex- .osives such as nitroglycerin or non-explosive igagents, for example ammonium perchlorate,

Jtassium perchlorate, sodium nitrate, blends of )dium and ammonium nitrate, etc. ,As has been ated, particular advantage is found in its inlusion in sensitized ammonium nitrate blastig agents of a low degree of-sensitivity, such that my cannot be detonated by one or more comiercial blasting caps. Such compositions are rdinarily packed into Watertight containers at igh density, for example above 1.0. It is imporant with such compositions to control the ensity closely, in order thatthey shall remain Jfficiently sensitive to propagate the explosion 'hen this has been once initiated and that at he same time they shall not lose their superior afety properties and become detonable by rela- .vely weak primers.

The inclusion of an organic low density maerial, such as a meal or flour, is definite in its ffect on the density of the explosive composiion but, as already pointed out, introduces some .ammability hazards. Such low density ingreient is ordinarily in finely divided form and as uch as is quite reactive with inorganic oxidizng agents. While such blends are stable at ordi.

.ary temperatures, more elevated temperatures,

.re often experienced during manufacture and iandling. In the case of ammonium nitrate ompositions that are packed in metal cans, for ixample, the sealing of the open end of the can .fter loading requires high temperatures, as in he soldering operation. When organic meals ,re' used, local burning of the charge is a definite lazard.

The .use of the inorganic expanded hydrated .ilicate in relatively finely divided form, in ac- :ordance with the present invention, not only gives all the advantages of .densitycontrol obained by the employment of organic meals but it thesame time introduces no safety hazards; n fact, its presence improves the safety prop- :rties. The material particularly favored for iuch use comprises the mineral vermiculite which has. been expanded by subjection to high emperatures. vermiculite is an alteration prodnot of mica and in composition is a complex hydrated aluminum-iron-magnesium silicate. It possesses the unusual property of exfoliating or expanding when heated to high temperatures, due to the fact that it normally is made up of extraordinarily large'numbers of layers per inch with a very small amount of water between each layer.

When subjected to high temperatures, the water becomes converted to steam, whereby the flakes expand into cellular grains of many times their original size. During this expansion, a great number of closed air cells are formed and the entrapped vair'insures its permanent low density. Other, normally anhydrous silicious materials, kieselguhr for example, do not possess this prop- 1 erty, and ;do not function in the manner described] for expanded vermiculite. The material as used will desirably have an apparent den's'ityof around 016 gram per cc. or less and a degree of fineness such that it will all pass a G-mesh and be largely held on'a' I l-mesh screen.

The water contentshould be low.

While various explosive compositions embodying the ingredients mentioned are suitable, we find a desirable'mixture to comprise more than 50% ammonium nitrate, between 0.5 and 10.0% of a normallysolid paraffin hydrocarbon, be-

7 tween 0.5- and 10.0% of an aromatic nitrocompound, and between 1.0 and 8.0% of'vermiculite in expanded form; Dinitrotoluene will be a satisfactoryaromatic nitrocompound, or a blend of nitrotoluenes.

The invention has been described at length in the foregoing. It will be understood, however,

that many variations may be introduced in compositions used, procedures followed, or types of explosive compositions, without departure from the scope of the invention.

I intendto be limited, following claims.

I claim:

1. A high velocity detonating explosive conprising morethan 50% ammonium nitrate, be-

tween 0.5'and 10.0% of a normally solid paraflin hydrocarbon, between 0.5- and 10.0% of a normally solid aromatic nitrocompound, and between 1.0 and 8.0% of vermiculite in expanded form,

AUSTIN MAURICE CUMMINGS.

REFERENCES orrnn The following references are of record in the file of this patent:

,. UNITED STATES PATENTS Number Name Date 1,743,744 Winkelmann Jan. 14, 1930 1,881,307 Bashford' Oct. 4, 1932 1,964,222 Scott June 26, 1934; 1,992,217 Kirst Feb. 26, 1935 Watts Mar. 8, 1949 therefore, only by the 

1. A HIGH VELOCITY DETONATING EXPLOSIVE CONTAINING ONLY NORMALLY SOLID INGREDIENTS AND COMPRISING AMMONIUM NITRATE IN AN AMOUNT, GREATER THAN 50% OF THE COMPOSITION, AT LEAST ONE NORMALLY SOLID ORGANIC SENSITIZING AGENT FOR THE AMMONIUM NITRATE, AND BETWEEN 1.0 AND 8.0% OF VERMICULITE IN EXPANDED FORM. 